1. Field of the Invention
This invention relates to polyester molding compositions and particularly to flame stabilized polyester molding compositions. This invention is particularly directed to the flame-stabilization of polyesters derived from an aromatic dicarboxylic acid halide or ester and an aliphatic diol having more than two carbon atoms in the chain. This invention is particularly directed to self-extinguishing flame-stabilized molding compositions containing 1,4-bis-(.beta.,.gamma.,.gamma.-trichloroallyl)-2,3,5,6-tetrachlorobenzene and a synergistically active quantity of an additional substance such as an antimony or boron compound.
2. Discussion of the Prior Art
On account of their attractive characteristics, thermoplastic polyesters, especially the polyalkyleneterephthalates, are being used to an ever increasing extent in many applications in mining, construction, the electrical industry and in textiles. Of growing importance are especially those types of polyester which are constructed on the basis of aromatic dicarboxylic acids or their polyester-forming derivatives, and aliphatic diols having more than two carbon atoms, particularly polypropyleneterephthalates or polybutyleneterephthalates. Such polyester molding compositions can be made into finished products by conventional methods, in extruders for example. They are especially well suited for the manufacture of injection molded products.
Their use is limited in many applications by the fact that they are relatively easily combustible. There has been no lack of attempts to make polyesters more resistant to flaming and combustion by the addition of appropriate agents. In addition to inorganic compounds, such as borates and aluminum hydrates, for example, organic sulfur, phosphorus and halogen compounds have been used as flameproofing agents. Many of these compounds are difficult to prepare, expensive, and of such poor effectiveness that great amounts of them have to be added to the polyesters in order to achieve a satisfactory effect.
The known flameproofing agents have proven unsuitable especially for polyesters on the basis of aromatic dicarboxylic acids or their polyester-forming derivatives and aliphatic diols having more than two carbon atoms. They often have the disadvantage of being not particularly compatible with the polyesters, this being manifested by the fact, for example, that "chalking" occurs in the finished products. Even during fabrication, decomposition products are frequently formed which corrode the apparatus and have an adverse effect on the characteristics of the molding compounds. It has also frequently been found that the volatility of the substances known hitherto is excessive, which results in a great hazard to health due to the formation of vapor during fabrication.
It has, therefore, become desirable to provide a self-extinguishing flame-stabilized polyester molding composition and it has become particularly desirable to provide a flame-stabilizing agent that can be readily incorporated into the polyester composition without chalking. It has also become desirable to provide a flame-stabilizer for a polyester molding composition which does not provide decomposition products which can corrode and foul the apparatuses used to make final molded articles. It has also become desirable to provide such a substance which does not have a high volatility and is not injurious to health.